Method and apparatus for transmitting and receiving sound-waves through ground.



a; A. Pesse-Num. METHOD. ANU APPARATUS FOR TRANSMITTING ANU RECEIVINGSOUND WAVES=THROUGH GROUND.

I Patented June 25, 1918.

2 SHEETS-SHEET l.

APPLICATION FILED OCT. 7. 1915- IIN H @gis y 4f A R. A. FESSENDEN.'Msuoo AND APPARATUS Foa TRANsMnTmG AND REEIVING souNu wAvvsHnouGHGnouup..

Patented M625, 1918.

2 SHEETS-SHEET 2.

APPLICATIONV FILED OCT. 7. |915.

UNITED STATES PATENT OFFICE.

-TEGINALD A. FESSENDEN, F BROOIILINE, MASSACHUSETTS, .ASSIGNOR TOSUBMARINE SIGNAL COMPANY,v OF PORTLAND, MAINE, A CORPORATION OF MAINE.

METHOD AND APPARATUS FOB TRANSMITTING AND RECEIVING SOUND-WAVES THROUGHGROUND.

'Specification of Letters Patent.

Patented June 25, 1918.

Application led October 7, 1915. Serial No. 54,556.

To all whom t may concern.'

Be it known that I, REGINALD A. FEssEN- DEN, a citizen of the UnitedStates, residing at Brookline, in the county of Norfolk and State ofMassachusetts, have invented new and useful Improvements in Methods andApparatus for Transmitting and Receiving Sound-Waves ThrougnGround, ofwhich the following is a specification.

This application is a continuation in art of my application Serial No.744,793, led January 29, 1913, now Patent No. 1,207,388, dated Dec. 5,1916.

This invention has for its object the transmission and receipt of soundwaves or impulses through the ground; also the determination of thedirection of transmission of said Waves or impulses; also thedetermination'of the location of the place of transmission of said wavesor impulses, also the elimination of disturbing waves or impulses.

This method differs from all methods heretofore used in signalingthrough the earth in that the signal-producing or receiving instrumentis not in such direct contact with the earth as to vibrate with the samephase or amplitude as the earth itself at the transmitting or receivingpoint and that an additional sound-receiving element is introduced, thatis, the water or anchor which forms an intermediate element to be usedbetween the vibratory diaphragm or corresponding element of thesignal-producing or receiving element and the ground contact, therebyavoiding losses from reflection and from the bending and irregulartravel of the sound waves, and also performing other useful functions,for example, enabling the true direction of the sound to be obtained andamplifying by mechanical resonance, or other advantages as hereinafterset forth.

There are in addition other novel features hereinafter set forth anddescribed.

In the drawings- Figures 1 and 2 illustrate diagrammatically twoarrangements of apparatus for carrying out my invention, combined sendmgand receiving stations being shown;

Fig. 3 is another form of sending device;

Figs. 4 and 5 show diagrammatically a. means.,for determming thedirection from which4` sound is received; e

Fig. 6 being a top view of the sighting device shown therein, taken online 6-6 of Fig. 4.

In Fig. 1, 13, 13, 14, 14, is the surface of the ground. 23, 24 are uidtight tanks, of cement or metal, or hewn in the rock, or dug in theground. They are filled with water or other uid, such as oil,.or with acombination of fluids such as water and glycerin, or solutions, such asthat of carbonate of soda in water. The tank is preferably placed in wetground, or the ground is wetted so as to make ood physical contactbetween the walls of t e tank and the surrounding ground, and the wallsof the tank are preferably so arranged as to transmit sound freely, forexample, if cement is used, the rock of the cement should not be soundabsorbent or have a velocity of sound transmission `differing greatlyfrom that of the cement itself.

The tanks are preferably covered over to prevent evaporation, by covers8 and 9.

11, 12 are devices for producing and receiving sounds, and as shownrepresent oscillators, of the type described in applicants U. S. LettersPatent No. 1,167,366. They are immersed in the tanks preferablydiaphragm downward. 15, 16 are two-way switches for connecting the leadsof the oscillators to the alternating current dynamos 19, 20, andtelegraph keys 21, 22, when the oscillators are used as sendinginstruments or to the telephone receivers 17, 18 when the oscillator ist0 be used as a receivin instrument.

en the operator at oscillator 11 wishes to telegraph, the switch 15 isthrown so as to connect the leads of 11 to the key 21 and the dynamo 19,and the operator at oscillator 12 throws the switch 16 so as to connectthe leads of 12 to the telephone receiver or other electro-ma eticmechanism 18.

As will be un erstood by those skilled in the art telephone transmittersmay be substituted for the keys 21, 22 and storage batteries for thegenerators 19 and 20 if it is desired to vary the resistance in thecircuit instead of making and breaking it.

Fig. 2 shows an alternative arrangement in which the sound producing andreceiving devices are supported above the surface of the ground thoughthey may be supported in trenches or elsewhere. In this case each device11,.12 is mounted on a rod or wire 29, 30, which in turn is supported byscrew anchors 25, 26, 27, 28. This mounting is especiall Vada ted totransmitand receive longitudmal vibrations while the mounting of Fig. 1is especially adapted to transmit and receive vertical vibrations.

In the construction of Fi 2 the vibrations originating in the osci latoror other instrument are especially lateral or horizontal vibrationswhich are primarily transmitted by the rod 29 and anchors 25 and 26 tothe earth and are in turn picked up by the anchor 27 and delivered bythe rod 30 to the oscillator 12 and the recording cr indicatinginstrument such as the receiver 18. In this case the sounds are receivedmainly from two directions determined by the line in which the twoanchors are placed.

In this arrangement the vvibrations produced and receivedby theoscillators arel lateral indirection, and the reception is to aconsiderable extent dlrectional, z'. e.,

sounds are not received from all directions but only from twodirections, determined by the line in which the two anchors are placed.

Fig. 3 shows another type of sound producing apparatus which may be usedin place of the oscillator in which 31 is a diaphragm, preferably ofsteel or duralumin, to the center of which is attached a wire or rod 29,the other end of said wire or rod being attached vto the bar 34 which issupported on rods 32, 33 attached to the diaphragm 31. The diaphragm isset in vibration by tuning the wheel 35 as shown in applicantsapplicati'pn, Serial No. 400,134, filed October 27, 190

In Fi 4 and 5 arehshown the apparatus and met od of detecting thedirection from which the sound waves or impulses are transmitted. Forexample, in time of war this apparatus may be placed in a trench and byits means the direction in which the enemy is mining or counterminingmay be determined.

Here 52 is the level of the bottom of the trench. 51 is a pail of watersunk in the.

ground the ground around the pail being preferably wetted so as to makegood physical contact between the pail and thevground. 40 is a socketmade of sound-insulating material such as lead, and mounted on legs, forexample, on a tripod or the like which rests on the bottom of the pail.The rod 41 has its lower end in the socket 40 so that rod 41 can rotateabout a vertical axis. The rod 41 and the bars 42, 43, 44, are attachedto each other by the joints 45, 46, 47, 48, permitting movement in avertical plane. 49, 50 are sights, 50 being attached to the bar 44 whichis extended above the joint 28 and 49 being attached thereto by the bar49".' A horizontal sight is obtained by sighting along 49 and a Verticalsight by sighting along 50 as below described.

36, 37 ,are two oscillators or microphones shown as microphones)attached to the ends of the bar 43 with their diaphragms pointingr inthe same direction. 39 is a differentially-wound telephone,fa lead fromone winding of which is connected to one of the microphones, the leadfrom its other winding being connected to the other microphone. Theother leads of the telephone are attached to one side of the battery 53and the other lead of each microphone to the other side of the battery.

Assume irst that the'ditferential windings are connected so as to opposeeach other, which is the generally preferred way. Then the soundstraveling through the ground must reach both microphones 36, 37, atexactly the same instant if the current fluctuation produced by thesounds in micro hone 36 is to annnl the effect of the current uctuationproduced by the sounds in microphone 37. This will occur whenthe bar 43and therefore the bar 44 is at right angles to the direction from whichthe sound is proceed- If the differential windings are connected so asto assist each other, then when the bars 43 and 44 are at right anglesto the direction of the sound the sound will be a maximum, but as it isharder generally to locate the exact maximum than the exact minimum, aswell as for other reasons, it is preferred to connect the differentialwindings so as to oppose each other.

In operation, the deviceJ is placed in the pail 51 in the bottom of thetrench, the pail being filled with water or oil and the 'bars 43, 44 areplaced horizontally, as shown at Fig. 4. The rod 41 with'its attachmentsis then rotated around its vertical axis until the sound which strikesthe microphones disappears or becomes a minimum. This will be at twopositions, 180 degrees from each other, i. c. when the microphones pointdirectly toward or directly away from the source of sound. The positionin which the microphones point toward the enemys trench will be the oneto take. This gives lio 'the vertical angle or the horizontal directionfrom which the sound is coming. This direction is fixed by sghtingalonthe sight 50, and is marked on the wall o the trench.

Then the rod 41 is rotated through 90 dcgrees, andthe bars 43,44 aretilted as shown 1n Fig. 5,y till the sound becomes a minimum again. Thenby sightin along the sight 49, ip of the direction from which the soundcomes is located, and having therefore both the direction in thehorizontal plane and. the dip, the observer has the exact direction fromwhich the sound is roceeding.

y taking another observation at a point a short distance along thetrench,.say 10 yards away, the location from which .the sound isproceeding may be determined in the same way, and its place of originwill be the point at which the two lines of direction, so determined,meet, and its distance can be readily calculated.

Where the sound has a definite wave lengthor' a strongly marked comonent,`

there will Vbe several partial minima, ut the true minimum is easllydetermined as it is the strongest marked, and the presence of I theother minima instead of being a detriment is an assistance, since itmakes the change in intensity per degree of angular' movement oftheapparatusmore marked.

The use of the aprparatus shown in Figs.

1 and 2 is not con ed to telegraphing between two points inland, as onepoint may be inland, for example, inside a coast defense fortification,and the `other. station may be `on a battleship 8 carrying an oscillator7 at some point off the coast.

What I claim as my invention is 1. A signaling means comprising aliquidy body inserted in the earth, and means in operative relation tosaid liquid body and adapted to set up vibrations therein whereby jsignals may the earth.

2. That `\method of receiving sounds through the earth which consists insetting up in a liquid body in operative connection be sent-and receivedthrough with the earth mechanical vibrations originating in the earthand transforming said vibrations into electrical undulations.

3. Means for transmitting and receiving sounds through the earth,comprising a liquid body inserted in the earth and adapt-y ed to be setin vibration, and signaling means in contact with said liquid body.

4. A method of signaling whichcomprises originating vibrations in aliquid body in "vibrations in a second liquid body. a contact with thelground and transforming contact with the ground and receivin said 1nsaid vibrations into electrical impulses. 5. A method of signaling whichcomprises originating vibrations in a liquid body in contact with thegroundand causing said vi- Il brations to lpass through the ground toreceiving mec anism also located in a li uid body and transforming saidvibrations into electrical undulations.

6. Apparatus for use in detecting or 10 transmltting earth vibrationscomprising an electrical apparatus adaptedfto produce in an electriccircuit.currents congruent with the earth vibrations, and anintermediate sound-conducting element in good conductive relationshipwith the earth and said electrical apparatus adapted to produce adifference of phase in the vibrations at several rts of the apparatus.

.7. a signaling mechanism, a liquid cont'ainer and a signaling.mechanism located therein, said liquid container being sunk in the earthand being maintained in close andl intimate physical contact therewith.

8. In a signaling mechanism, a liquid container and a signalingmechanism located therein, said container being sunk in the ground, saidground being dampened and in prlsing a liquid container sunk in theground and in close physical contact therewith.

11. The a paratus above described for determining the direction andlocation of noises which consists in two sound-receiving'. 'mechanismsand means whereby they may be rotated about an axis, and liquid meansfor connecting physically said mechanisms with the ground.

12. The apparatus above described for determining the Vdirection andlocation of noises, which consists in two sound-receiving mechanisms andmeans whereby they may be rotated about a vertical axis, and meanswhereby they may be rotated about a horizonal-axis, in combination Vwitha liquid container sunk in the ground and in close` ,physical contacttherewith in which said sound 12e receiving mechanisms aresubmerged.

'13; VThe apparatus above described for determining lthe direction andlocation of noises, which consists in two sound-receiving mechanisms andmeans whereby they may be rotated about a vertical axis, and meanswherebyv they may be rotated about a horizon` tal axis, and liquid`vmeans whereby a good.

physical contact -is made between said mechanisms and the ground.

14. A signaling system comprising a container sunk in the ground andfilled with 6 liquid,v a transmitter andreeeiver submerged in the liquidin said container, and a second container filled with liquid and havinga transmitter and receiver submerged in said liquid whereby the path ofthe vibrations proceeding from either transmitter will be 10 boththrough. the\ground and also through liquid.

REGINALD A. FESSENDEN.

